Working of titanium



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United States Patent 2,885,838 WORKING 0F TITANIUM Douglas E. Waite andRoyden C. Rinker, Alliance, Ohio, assiguors to Armour and Company,Chicago, Ill., a corporation of Illinois No Drawing. Application May 9,1956 Serial No. 583,624

15 Claims. (Cl. 51-281) This invention-relates to an improvement in theworking of titanium metal. In one of its aspects, this invention relatesto an improvement in .the abrading of titanium metal and its alloys. Inanother of its aspects, this invention relates to a method forincreasing the working life of an abrasive article when used forabrading titanium and its alloys.

In spite of its wide occurrence, titanium has not been used as astructural metal until very recently, principally because of thedifficulty of extracting it from its ores. Although titanium has manydesirable properties for certain uses, the metal was not commerciallyavailable until 1948 and then only in small quantities at high prices.

During 1954, titanium metal production was expanded at a phenomenalrate, despite continuing high prices.

Owing to what must still be considered limited supply, the presentapplications of titanium are principally for the military, particularlyin jet aircraft, although active preliminary investigations are beingmade in the automotive and commercial aircraft industries of theapplicability of titanium in products for civilian use. The uses oftitanium and its alloys are a result of a unique combination ofproperties, namely, light weight, high strength, and good corrosionresistance. At intermediate temperatures, titanium offers weight savingsover both alloy steel and alloy aluminum.

Manufacturers of both airframes and aircraft power plants believetitanium alloys will find expanded use in compounds exposed totemperatures as high as 450 C. A few of the items being considered bythe airframe producers are skin, fire-walls, landing gear components,hydraulic tubing, exhaust shrouds, oil and fuel tanks, nacellestructures, fasteners, and engine-supports. In gas turbine power plants,compressor discs, compressor blades, compressor housings, retainingblades, retaining rings and fasteners are being fabricated. Otherapplications of the favorable strength-weight ratio are found wherepower loss through momentum is involved. Reciprocating equipment, steamturbines, gas turbines, textile machinery, and Diesel engines are fieldswhere titanium metal will find application.

Because of its excellent corrosion resistance, titanium can be appliedin the chemical and allied industries, in basic equipment such asautoclaves, heat exchangers, agitators, lined tanks, and the like.

It will be noted that all of the aforementioned uses require that themetal or its alloys be worked and machined in one way or another.Unfortunately, the physical properties of titanium give rise to specialproblems in machining and related operations. First of all, the metaland its alloys seize and gall upon other metals and hard substances.This is believed to be caused by a tendency for titanium to dissolve orspecifically adhere to hard steel and carbide cutting tools and toabrasives such as aluminum oxide, silicon carbide and other commonabrasive substances] This is illustrated by the fact that it is possibleto mark glass with moistened titanium. Further, it work-hardens rapidlyand glazes when light cuts are at- Ice to improvements in the grindingof titanium metal andits alloys. Grinding is essentially an abradingoperation achieved by means of abrasive grits in the form of wheels,belts, discs, and the like. The fundamental difiiculties in titaniumgrinding are the high mutual solubility of titanium in most other metalsand refractories or abrasives at elevated temperatures, and the veryhigh temperatures occurring in chip-forming processes. The individualgrinding grits are subjected to a combination of high temperature andthe severe solution action of titanium. This results in direct attritionand dulling of the abrasive grits by dissolving, or in solution-bondingof titanium to the abrasive grits, causing capping and resultantfracture of the grits. In accordance with the present invention, we havediscovered that when certain chemical compositions, which will be morefully described hereinafter, are employed in working titanium metal andits alloys, the aforementioned difficulty can be substantiallydiminished with considerable lengthening of tool and abrasive articlelife.

It is, therefore, a general object of the present invention to providean improvement in the working of titanium metal and its alloys.

It is another object of this invention to provide an improvement in thegrinding or abrading of titanium metal and its alloys.

Still another object of the present invention is to pro-- vide a methodfor increasing the working life of an abrasive article or cutting toolwhen used for abrading or machining titanium metal and its alloys.

Further and additional objects of the present invention. will becomeapparent as the specification proceeds.

Broadly, our invention involves working titanium metal or alloy in thepresence of a composition consisting of a hydrocarbon or glyceride oilcontaining between about 25 and 45 weight percent of a chemicallycombined halogen, such as chlorine, bromine, fiuorine, or iodine. Foreconomic reasons, the preferred halogen is chlorine. These chemicals arenot new per se, and can be readily prepared by reacting the halogen withthe basic oil in the presence of a catalyst or ultraviolet light withheating when necessary. For example, one preferred composition isprepared by bubbling chlorine gas through tallow in the presence ofultraviolet light at a temperature of about -150 C. until the desiredweight percentage of chlorine has been absorbed. Although for practicalreasons, it may be desirable to strip the hydrochloric acid formed inthe reaction from the resulting oil, from a functional standpoint asrespects its use during the working operation, this is not necessary. Infact, in some instances,

the presence of the acid actually promotes the effectiveness presentinvention.' Hydrocarbon oils such as minerall oil, parafiin oil and thelike halogenated to about 25 toz45 Weight percent of halogen can also beemployed eifectively.

In practising our invention, the halogenated oils can be applied eitherto the work itself or to the tool or abrasive article. Generally, it isdesirable to heat the oil. so that it is in a fiowable state. The oil isemployed in. its full concentration rather than in a diluted or cutbackform, and can be continuously circulated during the working operation.It is also possible to employ these halogenated oils in the form ofsticks or bars which when applied to the work or abrasive article arespread out. Replenishment of the chemical as used is, of course,required,

We are unable to explain with certainty how or why these halogenatedoils function, and do not want to be bound by any particular theory ofoperation. It is believed that there is a controlled release of chlorinegas which reacts with the titanium metal to form a halide which obviatesor diminishes considerably the solutionbonding effect of the titaniummetal on the refractory abrasive grit or metallic cutting tool.

Although chlorinated hydrocarbons such as carbon tetrachloride and otherlow molecular weight halogenated compounds have been employed asgrinding aids. These compounds are themselves highly toxic and give ofieven more highly toxic pyrolysis products. Such is not the case with thelubricants of the present invention. Further, other previous lubricantcompositions contain very small quantities of halogen and are used asdispersions in water requiring much more costly waterproof abrasivearticles. Employing the lubricants of the present invention,non-waterproof abrasives can be used with excellent results.

The improvements of operation achieved in accordance with our inventionare quite outstanding. For example, the working life of abrasive beltswhen used for abrading titanium metal and its alloys have been increasedfrom at least 50 to 3,000 percent. Also, there has been a substantialreduction in the micro inch finish of. the abraded metal or alloy.

Our invention can be further understood with reference to the followingexamples:

Example! A series of comparative tests employing a number ofconventional grinding aids as well as a halogenated oil of the presentinvention were made by abrading a bar of commercially pure titaniummetal /s x 4" x 16" on a platen grinder at 1800 surface feet per minutefor a period of two minutes with waterproof silicon carbide cloth belts4" x 96 /2" having a grit size of No. 120. The grinding aids wereapplied directly to the metal and the amount of metal abraded during thetwo minute period was measured by weight difference.

Employing a percent aqueous solution of sodium nitrite, 2.73 grams oftitanium metal was abraded in the two minute period.

Employing a commercial grinding aid comprising a soluble oil containingsodium nitrite and nitrate, as a water suspension containing 1 part ofoil in 100 parts of water, 4.73 grams of titanium metal was abraded inthe two minute period.

Employing a commercial grinding aid comprising a mineral oil containingbetween 1 and 2 percent sulfur and. between 2 and 3 percent of chlorine,8.57 grams of titanium metal was abraded in the two minute period.

Employing a commercial grinding aid comprising a soluble oil containingabout 2 /2 percent sulfur, as a water suspension containing 1 part ofoil in 25 parts of water, 6.45 grams of titanium metal was abraded inthe two minute period.

Employing a. commercial grinding aid comprising a soluble oil sold underthe trade name Staysoll 77, as a water suspension containing 1 part of'oil in. 16 parts ofiwater, 4.55 grams of titanium metal was abraded inthe two minute period.

Employing as a grinding aid a product of the present inventioncomprising a mineral oil containing between about 25 and 45 weightpercent of combined chlorine, 14.25 grams of titanium metal was abradedin the two minute period.

Example II A series of tests was made abrading commercially puretitanium metal as in Example I, using abrasive belts of No. 36 gritsilicon carbide on a backstand with an durometer serrated contact wheel.The grinding aids were applied directly to the metal and the amount ofmetal abraded during a 15 minute period was measured by weightdifference.

When no lubricant was employed a total of 45 grams of metal was abradedduring the 15 minute period.

When employing the best of the commercially available grinding aids,which was a mineral oil containing between about 1 and 2 percent sulfurand between about 2 and 3 percent chlorine, 56 grams of titanium metalwas abraded during the 15 minute-period.

When employing a product of the present invention comprising a mineraloil containing between about 25 and 45 weight percent of combinedchlorine, 92 grams of titanium metal was abraded during the 15 minuteperiod.

Example III In an actual commercial plant operation propeller blades ofa titanium alloy were abraded with No. aluminum oxide grit belts havingbrushed thereon at room temperature a mineral oil containing betweenabout 25 and 45 weight percent of combined chlorine as' a grinding aid.The number of propeller blades that could be abraded employing one beltwas 3V2 times greater than when a tallow stick was employed as agrinding aid.

Example IV In another commercial plant operation compressor blades of atitanium alloy were abraded with No. 120 aluminum oxide grit belts. Amineral oil containing between about 25 and 45 weight percent ofcombined chlorine at a temperature of about 120 F. was flowed onto thepoint of contact between the abrasive article and the work being ground.The number of blades that could be abraded employing one belt was 9times greater than when a conventional petroleum oil was employedas agrinding aid.

Example V In still another commercial plant operation a titanium alloywas drilled with holes 0.225 inch in diameter which were thenreamed-employing as a lubricant for the-reaming a mineral oil containingbetween about 2 5 and 45 weight percent of combined chlorine. Thisoperation resulted in an out-of-round of 0.0001 inch ascompared to anout-of-round of 0.003 when employing a conventional petroleum oil as alubricant.

It will be appreciated by those skilled in the art that modificationscan be madein the procedures and compounds disclosed without departingfrom the spirit and scope of the invention.

We claim:

1. In a process wherein a metal selected from the group consisting oftitanium metal and its alloys are worked, the improvement whichcomprises working said metal in the presence of a composition consistingof a compound selected from the group consisting of hydrocarbon oils andglyeeride oils containing between about 25 and 45 weight percent of'chemically combined halogen.

2. A proccess according to claim 1 wherein the composition employed is ahalogenated mineral oil.

3. A process according to claim 1 wherein the compound employed isachlorinated mineral oil.

4. A process according to claim 1 wherein the'compound employed is achlorinated glyceride oil.

5. A process according to claim 1 wherein the compound employed ischlorinated tallow.

6. In a process wherein a metal selected from the group consisting oftitanium metal and its alloys are abraded, the improvement whichcomprises abrading said metal in the presence of a compositionconsisting of a compound selected from the group consisting ofhydrocarbon oils and glyceride oils containing between about 25 and 45weight percent of chemically combined halogen.

7. A process according to claim 6 wherein the compound employed in ahalogenated mineral oil.

8. A process according to claim 6 wherein the compound employed is achlorinated mineral oil.

9. A process according to claim 6 wherein the compound employed is achlorinated glyceride oil.

10. A process according to claim 6 wherein the compound employed ischlorinated tallow.

11. A process for increasing the working life of an abrasive articlewhen used in the abrasion of titanium metal and its alloys whichcomprises applying to the abrasive grits at their point of contact withthe metal a composition consisting of a compound selected from the groupconsisting of hydrocarbon oils and glyceride oils containing betweenabout 25 and 45 weight percent of chemically combined halogen.

12. A process according to claim 11 wherein the abrasive article is anabrasive wheel.

13. A process according to claim 11 wherein the abrasive article is aflexible coated abrasive in the form of a belt.

14. A process for increasing the working life of a coated abrasive beltwhen used for abrading titanium metal and its alloys which comprisesapplying to the abrasive grits at their point of contact with the metala mineral oil containing between about 25 and weight percent ofchemically combined chlorine.

15. A process for increasing the working life of a coated abrasive beltwhen used for abrading titanium metal and its alloys which comprisesapplying to the grits at their point of contact with the metal tallowcontaining between about 25 and 45 weight percent of chemically combinedchlorine.

References Cited in the file of this patent UNITED STATES PATENTSChurchill et a1 Dec. 12, 1944 Rocchini et a1. Nov. 7, 1950 OTHERREFERENCES

1. IN A PROCESS WHEREIN A METAL SELECTED FROM THE GROUP CONSISTING OFTITANIUM METAL AND ITS ALLOYS ARE WORKED, THE IMPROVEMENT WHICHCOMPRISES WORKING SAID METAL IN THE PRESENCE OF A COMPOSITION CONSISTINGOF A COMPOUND SELECTED FROM THE GROUP CONSISTING OF HYDROCARBON OILS ANDGLYCERIDE OILS CONTAINING BETWEEN ABOUT 25 AND 45 WEIGHT PRECENT OFCHEMICALLY COMBINED HALOGEN.